1. Filed of the Invention
The present invention relates to a refrigerator, more specifically to a gas cycle refrigerator consisting of a compressor, a gas expansion vessel, a heat accumulator, and a switch valve. In a gas cycle refrigerator of this type, for instance helium gas pressurized by the compressor is introduced via the switch valve into the gas expansion vessel, where the pressurized gas expands and cools to a very low temperature of, say, about 20.degree. K.; the heat accumulator is maintained at the very low temperature by the cold gas so that refrigeration can be provided for some object to be refrigerated; the gas is then returned via the same switch valve to the compressor, this cycle being repeated.
The gas expansion vessel comprises a cylinder and a displacer piston slidably mounted within the cylinder so that a plurality of gas expansion chambers are defined between the cylinder and the displacer within the cylinder. The gas expansion chambers communicate with one another through the heat accumulator.
One of the gas expansion chambers located at one end of said cylinder is connected to the switch valve and in operation this chamber remains warmer than the other chambers, usually at about the room temperature.
2. Description of Prior Art
Usually in the conventional gas cycle refrigerator of this type, when a pressurized gas from the compressor is supplied via the switch valve to the gas expansion vessel, the pressures at both ends of the displacer will rise, but thereby a pressure loss will occur in the heat accumulator and in consequence the pressure rise at the low-temperature end of the cylinder will be delayed as compared with that at the high-temperature end of the cylinder. In this gas supply stage the displacer has to be moved from the low-temperature end to the high-temperature end, but the difference in the rate of pressure rise will hinder the required movement of the displacer. In the stage of the working gas being returned to the compressor from the gas expansion vessel, the pressure loss in the heat accumulator likewise results in a difference of pressure fall at both ends of the displacer which will hinder the displacer movement. In consequence a large force will be needed to drive the displacer.